What is the most efficient drip system setup for irrigating a tree in the desert?

Question

What is the most efficient (i.e., least water lost due to evaporation) drip system setup for irrigating a tree in the desert?

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I've seen some elaborate setups, like this:

But having it above-ground like this would seem to result in a lot of water loss via evaporation.

I've also seen soaker hose setups laid out in a spiral.

Or this:

This chart shows how many emitters I need:

However, can I get by with only a half-dozen or so emitters per tree, and just water longer? Should the emitter tubes be buried in the ground, or should they should poke into the ground?

Would this be good?:

Answer 1

Why not do what people in similar climates used to do for centuries? Use large flat rocks to conserve soil moisture. You can amend their methods to work with drip irrigation too if you wish. Use of natural materials, especially stone, is a feature of permaculture in dry environs. This method is still practiced today. It's just not that common since most people figure it's easier to bring water in than conserve it, or aren't even aware of this technique.

While the soil directly under the stones will heat up, the heat only extends a few inches down. Under that level, the soil tends to remain at an even temperature. Rocks take longer to heat up and maximum temperatures aren't reached till late afternoon. Heat stored is slowly released in both directions (into the air and into the soil) during the night. In deserts, nights can be quite cool since there's little moisture in air or soil to hold heat.

If you laid vegetative mulch around the tree (out past where the drip line would be in a few years), landscape fabric over that and then the flat rocks, you'd conserve water even better while discouraging even weeds from growing in the wetter soil around your tree. Then, whatever method you decide for watering your tree, you won't need to be concerned on water loss through evaporation.

Answer 2

I grew up in one of the hottest driest places in Australia. My mother still lives in this place... Adelaide, South Australia and she lives in a house on a quarter acre, surrounded by a large garden with no lawn. Most of her garden is watered by drip irrigation.

Two elements are essential for success.

• Adequate water to sustain plants during periods of dry weather, delivered over a period of time; and
• mulch across the top of the soil.

There are pros and cons for placing the watering mechanism both over the top of or under the mulch.

Pros and cons for placing drippers under the mulch

Pros: greater water absorption, less evaporation, less likelihood of physical damage,

Cons: difficult to inspect and maintain, can become clogged from soil and other material becoming embedded in dripper outlets.

Pros and cons for placing drippers over / on top of the mulch

Pros: easy to inspect and maintain, unlikely to become clogged from soil and other material.

Cons: slightly less water absorption, slightly greater moisture evaporation (both of which can be alleviated by watering in late evening), greater likelihood of physical damage.

The type and number of drippers required is dependent on a few factors, that include:

• type of soil, specifically how well it both absorbs and retains water;
• profile of soil, specifically how deep is the topsoil and what type/s of earth lie beneath;
• availability to source of reasonably priced water;

In my mother's situation, small plants are watered by one single point dripper unit and larger plants and trees are watered by two single point dripper units. The lines are active for about two hours and the drippers / emitters run at 3-6 litres per hour, depending on type. While this doesn't allow adequate water for plants to flourish, it is adequate for survival which in that environment during summer is far more important.

Of all the different options you've mentioned in your post, it's worth noting that time and money are usually also a consideration for most people.

Not just the time and money to set the system up but also to maintain it over the years of operation.

So hopefully this summary assists. If you need any clarification add a comment and I'll update my answer.